This application claims priority of German Application No. 101 13 943.8, filed Mar. 21, 2001, the complete disclosure of which is hereby incorporated by reference.
a) Field of the Invention
The invention is directed to a diode laser component with a diode laser bar on a mounting surface of a passive cooling heatsink and a cover element for the diode laser bar, wherein the heatsink and the cover element are constructed so as to be electrically conductive and contain recesses for fastening of elements.
b) Description of the Related Art
Solid heatsinks in which the cooling effect is brought about through heat conduction are typically used for passive cooling of high-power diode laser bars. However, if needed, a heat pipe structure can be provided, in addition, for passive convection evaporative cooling.
The object of the heatsink, aside from mechanical support, is above all to cool the high-power diode laser bar mounted on a mounting surface on its upper side. In this connection, it is especially important that sufficient heat spreading is ensured for increased cooling efficiency and that the steps taken in this regard can be reconciled with other requirements of a diode laser component. In particular, this concerns the use of collimating optics, if needed, and the supply of increasingly higher electric power. For reasons of space, the dimensioning of the heatsink should be determined by the measurements which, for thermal reasons, are required for the heat spreading of the energy loss. This applies in particular to the lateral dimension in the plane of the heatsink surface vertical to the radiating direction of the diode laser bar. However, care must be taken in this regard to ensure the thermal symmetry of the heatsink with respect to the diode laser bar because, otherwise, the diode laser bar would have warmer and colder areas during operation.
Heatsinks comprising electrically conductive material are usually fastened to a conductive base plate through which the current supply is effected. While the heatsink is constructed as anode (p-contact), the n-contact is produced through a cover of the high-power diode laser bar. When a plurality of diode laser components must be used in operation simultaneously, a design of this kind causes difficulties because of the preferability of an electric series connection whose demands on the power supply and electric supply lines are not as exacting as those of a parallel circuit.
It is the primary object of the invention to provide a passive cooling heatsink with improved heat spreading such that a diode laser component which uses a heatsink of this type has a thermally symmetrical and compact construction and can be used for multiple purposes, particularly as regards beam control and electrical circuitry.
This object is met according to the invention by a diode laser component of the type mentioned in the beginning in that the heatsink contains an area for heat spreading which is enclosed by material and surrounds all edges of the mounting surface, wherein the recesses for fastening the elements are arranged in the heatsink outside of this area.
A thermal symmetry guaranteed in this way ensures a uniform temperature distribution in the diode laser bar.
For purposes of unobstructed beam propagation, a bevel at a part of the heatsink located in front of the mounting surface in the emitting direction of the diode laser bar has an angle of inclination that is adapted to the radiating angle of the diode laser bar.
It is particularly advantageous for receiving optical imaging elements, e.g., collimating optics, when the heatsink contains a step between the mounting surface and the bevel, which step has a receiving surface extending parallel to the mounting surface. The projection of the heatsink protruding over the collimating optics has an added positive effect in that it protects the optics and the diode laser bar from mechanical influences.
A bore hole which receives a temperature sensor and which is adjacent to the area for heat spreading adjoins the mounting surface on at least one side in direction vertical to the emission direction of the diode laser bar.
The symmetric arrangement of temperature sensors on both sides of the diode laser bar and their proximity to the edge of the area for heat spreading are particularly advantageous. In this way, without obstructing the heat spreading area, detection of measurements coming close to the actual temperature ratios below the diode laser bar is ensured, and disturbances or defects in the diode laser bar can be deduced from the detected measurements by means of the symmetric measuring construction in case of a discrepancy between temperature measurements.
Therefore, one bore hole of a pair of bore holes in the mounting surface which serve to receive sensor elements for temperature measurement should be adjacent to and should adjoin the area for heat spreading at each side in a direction vertical to the emission direction of the diode laser bar, wherein the distances of the bore holes from the mounting surface should be identical.
Bore holes are advantageously arranged eccentrically in the heatsink and cover element on the side of the diode laser bar facing away from the emission direction for purposes of fastening electrical contacts.
On the one hand, this facilitates a series connection of a plurality of diode laser components and on the other hand provides for more flexible use when the cover element has a base surface and a top surface, both of which are suitable as connection surfaces for connecting to the heatsink. The bore holes which are arranged eccentrically in the heatsink and cover element can therefore be placed either next to one another in a direction vertical to the emission direction of the diode laser bar or coaxially one over the other, depending on the choice of connection surface.
Further, arranging the electric contacts in the back ensures that the electric supply lines are protected against damage by laser radiation and that the diode laser component remains compact itself without interfering with the heat spreading.
Very high currents (up to 100 A) can be supplied to the laser diode component when the bore holes for fastening the electric contacts are constructed as threaded bore holes by which pole pieces of power cables can be fastened by screws. In order to increase operating safety, the bore holes have different diameters so as to eliminate confusion.
The diode laser component is particularly suited to a potential-free construction; this applies to the individual element as well as to a series connection of a plurality of diode laser components, since the heatsink has separate areas for power supply and heat dissipation. While the heatsink can be fastened to a cooling plate by its base surface so as to be electrically insulated, the screw connection provided for one electric contact (p-contact) is positioned in a practical manner just like the screw connection at the cover element.
It is also advantageous when the heatsink and the cover element can be electrically short-circuited with one another, which can be achieved, e.g., by means of a detachable screw connection.
The area for heat spreading which is enclosed by material can comprise one material or different materials. The latter is especially beneficial when the area for heat spreading which is enclosed by material contains at least one graphite core which is enclosed by another heatsink material.
Also, it is advantageous when the mounting surface is arranged on a substrate which is provided as a material part of the heatsink and whose heat conductivity exceeds that of metals and which can also be subdivided into partial substrates.
A particularly advantageous heatsink can be constructed when copper tungsten or copper molybdenum is used as heatsink material in combination with the enclosed graphite core and when the mounting surface is arranged on a metallized substrate which is provided a material part of the heatsink and which comprises monocrystalline silicon carbide.
Finally, the cover element or the heatsink can be used to carry an evaluating device for detecting measurements, converting measurements and possibly also for storing measurements, so that unnecessarily long transmission paths are avoided.
The invention will be described more fully in the following with reference to the schematic drawings.